This invention relates to the preferential formation of and efficient recovery of alpha olefins by the employment of catalytic distillation in combination with olefin double bond isomerization (shifting of double bonds within an olefin molecule between internal double bonds and double bonds in the alpha position).
Heretofore higher olefins (4 carbon atoms per molecule and higher) have been formed by way of lower olefin (2 or 3 carbon atoms per molecule) oligomerization, see U.S. Pat. No. 2,943,125 to Ziegler et al.
Also heretofore alpha olefins (hereinafter a-olefins) have been oligomerized by using catalytic distillation, see U.S. Pat. No. 4,935,577 to Huss, Jr., et al.
Further heretofore the xcex1-olefin 3-methyl butene-1 (hereinafter 3MB1) has been formed by dehydration of isoamyl alcohol using base treated alumina.
Finally, U.S. Pat. No. 4,435,606 to Motz et al. heretofore taught the formation of olefins using aluminum alkyls and then transformation of the xcex1-olefins present, in part to internal olefins (olefin molecules with internal double bonds as opposed to olefin molecules with double bonds in the alpha position) using a conventional isomerization reaction. Motz et al. disclose that a conventional isomerization reaction carried out in a conventional isomerization reactor xe2x80x9crandomizes the double bond placement such that only about 2% alpha olefins remain.xe2x80x9d This is due to the chemical equilibrium constraints that exist at conditions that are present in a conventional isomerization reactor. By xe2x80x9cequilibrium constraintsxe2x80x9d what is meant is the balance between xcex1-olefins and internal olefins that a given isomerization reaction cannot exceed due to thermodynamic chemical equilibrium. In the case of the illustration of Motz et al. their conventional isomerization reaction reaches equilibrium of 2% xcex1-olefins, the remaining olefins in the conventional reactor being internal olefins, and maintains that relative equilibrium between xcex1-olefins and internal olefins throughout that conventional isomerization reaction. Thus, the amount of xcex1-olefins formed in the Motz et al. illustration is limited by reaction equilibrium constraints to 2% xcex1-olefins with the remainder of the olefins in the product being internal olefins.
In accordance with this invention xcex1-olefins are continuously formed using conventional isomerization catalyst and then promptly and efficiently removed from the reaction by employing that catalyst in a catalytic distillation column (tower).
By the method of this invention, the isomerization catalyst is employed in a distillation tower in known manner so that the xcex1-olefins are formed under distillation conditions that favor speedy removal of the just formed xcex1-olefins out of the isomerization reaction and out of the tower.
This overcomes the equilibrium constraints of the isomerization reaction as described hereinabove without eliminating the function thereof, and continuously drives the isomerization reaction toward the formation of ever more xcex1-olefins.
Thus, by this invention, xcex1-olefins are continually formed in a distillation tower, are promptly removed from the isomerization reaction locale in that tower (reactor) by the distillation conditions under which they were formed, and are just as promptly removed from that reactor and tower for efficient collection of same for further use. This invention thus makes use of the natural equilibrium drive of the isomerization reaction to continuously make xcex1-olefins by the continuous swift and efficient removal of xcex1-olefins from the distillation tower, the reaction never reaches, much less maintains, its natural equilibrium constraint between xcex1-olefins and internal olefins. This allows the overall conversion of internal olefins to far exceed that possible in a conventional isomerization reactor.